Radio proximity fuze



Oct. 13, 1964 Filed Dec. 4, 1950 FIG. 1.

l' 7.9 1 Ba 2 Sheets-Sheet 1 JOHN W. KYLE Gttomegs United States Patent 3,152,547 RADIO PROXEMITY FUZE John W. Kyle, Rochester, N.Y., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Dec. 4, 1950, Ser. No. 199,038 7 Cl. (Cl. 102-702) This invention relates to radio apparatus and in particular to radio-controlled proximity fuzes for projectiles.

Performance characteristics of radio-controlled proximity fuzes heretofore manufactured could not be predicted with certainty. It was not unusual for a large percentage of fuzes that had been stored for a few months in tropical climates to fail to fire. This failure to fire, or duddage, as well as premature detonations resulted from, among other reasons, both imperfect weatherproofing of and mechanical failure within the fuze. The hermetic sealing of the fuze casing was ineffective to entirely prevent entry of moisture, and under conditions of high humidity the plastic of nose tip of prior art fuzes transmitted sufiicient moisture to cause loss of sensitivity of the oscillator. The wax in which the electronic circuit assemblies were embedded had sufficiently high water absorption, and particularly water transmission through cracks, to cause both failure of the condensers of the amplifier and, in effect, overloading of the oscillator. This embedment material often softened sufiiciently at the temperature encountered within the fuze during the firing of a projectile to cause displacement of the electronic circuit components and their supports with consequent breakage of leads.

The nose of many fuzes heretofore manufactured was made of insulating material with an antenna in the form of an exterior conical metal cap, or nose piece, molded at the tip of the plastic nose to complete the ogival con tour of a projectile. The designation antenna will be used herein to refer to such a nose cap, although the casing of the projectile is in reality employed as an antenna with the radio frequency energy end-fed to the casing through the nose cap, i.e., currents are induced in the metal casing of the projectile causing it to radiate energy which combines with that from the nose cap to form the resulting pattern of energy in space. It is necessary to make a wire connection to the antenna cap, and in fuzes heretofore manufactured the heat developed in the flight of a projectile due to air friction against the exterior cap was often suflicient to open this connection. Furthermore the pawls of projectile hoists occasionally damaged the antenna cap while the hammer occasionally opened the antenna connection. The reduction in capacity coupling which resulted in other fuzes constructed with a small hemispherical antenna cap enclosed within a plastic nose greatly increased the radiation impedance and made it extremely diificult to match the oscillator to its shell load.

It is an object of the invention to provide a radiocontrolled fuze casing which is substantially impervious to moisture.

A further object of the invention is to provide such an impervious fuze casing which is divided into two separate compartments both of which are hermetically sealed.

Another object of the invention is to provide a radiocontrolled proximity fuze in which the subassemblies within the fuze are constructed with maximum weatherproofing.

A still further object of the invention is to provide a radio-controlled proximity fuze which can be stored for long periods of time in humid climates without failure of the condensers of the electronic circuit assemblies or "Ice appreciable variation in the electrical senstivity of the oscillator.

Still another object of the invention is to provide a radio-controlled proximity fuze in which the electronic circuit assemblies are supported with maximum shockproofing and strength so that duddage and premature detonations due to displacement of the components and mechanical failure under the centrifugal force, setback and thermal shock encountered in the firing of a projectile, or under the vibration caused by yaw in the flight of a projectile, are substantially eliminated.

It is also an object of the invention to provide an improved nose portion of a proximity fuze which will withstand the impacts imparted to a projectile in a hoist and air friction encountered in the flight of a projectile without damage to the antenna cap or opening of the antenna connection.

It is a still further object of the invention to provide a radio-controlled proximity fuze in which the antenna cap is completely shielded from the pawls and hammer of a hoist, from the blast of a gun, and from heat generated by air friction during the flight of a projectile, and yet the capacity coupling between the oscillator and its shell load is not appreciably reduced in comparison to proximity fuzes having exterior antenna caps.

It is also an object of the invention to provide an improved nose portion of a proximity fuze which, when assembled to a projectile, will not appreciably increase the radiation impedance into which the oscillator feeds above that of proximity fuzes constructed with exterior antenna caps.

Briefly, the nose portion of the casing of the fuze of my invention includes a hollowed conical nose tip formed of a suitable plastic, such as polytetrafluoroethylene, having high impact strength and substantially zero water absorption joined to a hollowed, frustrum-shaped, metallic intermediate member by a crimp joint which is impenetrable by moisture. The amplifier and thyratron circuit assemblies of the fuze are completely encased in a metallic housing and potted with a suitable plastic,

such as polyethylene, having substantially zero water absorption and a sufficiently high melting point to prevent softening at the temperature encountered within the fuze during the firing of a projectile. The oscillator is mounted upon this metal housing and potted with a similar plastic in a suitable cavity so that the resulting oscillator-amplifier unit is adapted to fit snugly within the hollowed nose portion of the fuze. The rear end of the oscillator-amplifier unit is sealed across the front end of the sleeve portion of the fuze casing by a crimp joint to provide a completely impervious enclosure within the sleeve for the battery and rear fitting of the fuze. A thin-walled conical metallic antenna cap is fitted tightly over the front of the oscillator-amplifier unit, and when this unit is inserted into the hollowed nose portion of the fuze, softened plastic is fed into the space between the oscillator-amplifier unit and the plastic nose tip to make all the parts of the nose portion substantially integral and thusminimize premature detonations due to microphonics generated by internal vibration. A gasket squeezed between the front edge of the sleeve and the intermediate member when the sleeve and nose portions are solidly screwed together forms an imperviable joint which seals off the nose portion from entry of moisture and offers a second obstruction to the entry of moisture into the sleeve of the fuze.

Other objects and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawing which forms a part hereof.

In the drawings:

FIG. 1 is a longitudinal cross sectional view through a radio-controlled proximity fuze embodying the features of the invention;

FIG. 2 is a longitudinal sectional view through the nose portion of the fuze shown in FIG. 1; and

FIG. 3 is an enlarged partial sectional view taken through the joint which hermetically seals the front of the sleeve portion and also through the joint between the sleeve and the front case assembly.

The fuze casing of the preferred embodiment of the invention illustrated in FIG. 1 of the drawing includes a hollowed, conical front case assembly lltl secured to a metallic sleeve 11. The front case assembly 10, which completes the exterior ogival contour of an ordnance projectile, comprises a hollowed, approximately conical, nonconducting nose tip 12 affixed to a hollowed metallic intermediate member 13. The intermediate member 13 is approximately frustrum-shaped, and a tubular flange 15 formed on the rear end thereof is provided with both an external thread 15 to engage a threaded ordnance projectile casing and an internal thread 18 which is adapted to engage an external thread 19 cut in the exterior periphery of the sleeve 11 near the front end thereof. A circumferential recess 21 of greater diameter than the minor diameter of the internal thread 18 is provided in the inner periphery of the intermediate member 13 in front of the internal thread 18 with the front radial face of said circumferential recess 21 extending further toward the axis of the intermediate member 13 than said minor diameter to form an annular radial shoulder 22 which is adapted to abut against the front end of the sleeve 11 when the nose and sleeve portions of the fuze are solidly screwed together.

The approximately conical nose tip 12 is constructed of a suitable plastic, such as polytetrafluoroethylene, having substantially zero water absorption, high impact strength, a low dielectric constant, and a low dielectric loss factor even at high frequencies. An annular groove 24 extending rearwardly parallel to the axis of the fuze casing is provided in the front edge of the intermediate member 13 to receive the rear open end 25 of the conical nose tip 12, and a lip 26 which forms the outer wall of the annular groove 24 is crimped against the open end 25 to secure the nose tip 12 to the intermediate member 13. A hermetic seal is thus effected at this joint which is substantially impervious to moisture. Although the wall section of the nose tip 12 is considerably thinner than in proximity fuzes heretofore manufactured in order to provide sufiicient room for the antenna cap, the nose portion of the preferred embodiment of the invention successfully withstands severe vibration, thermal shock, impact and hoist tests.

The electronic components of the amplifier and thyratron circuit assemblies are positioned within a plurality of parallel, approximately cylindrical, component holding cavities, e.g., subminiature type electron discharge tubes 28 and tubular resistors 29 within cavities 30 and 31 respectively, in an approximately cylindrical, nonconducting component holder 34 as disclosed in the application of Edgar H. McLaughlin, Serial No. 135,063 filed December 27, 1949, now Patent No. 2,994,806. The present invention is particularly directed to nonconducting means for supporting and enclosing the electronic circuit assemblies of the fuze. Although metallic supporting and enclosing means are utilized where shielding and exceptional strength are required, the means for directly supporting and enclosing the electronic circuit components are formed of a suitable plastic, e.g., polystyrene or polyethylene, which must possess excellent electrical, moisture and temperature properties, i.e., low dielectric constant, low water absorption, low loss factor even at high frequencies, and a sufficiently high melting point to prevent softening at the temperature encountered Within the fuze during the firing of a projectile or at the temperature at which the circuit assemblies are potted. The designation plastic suitable for electronic application will be used in the present specification to refer to a suitable plastic possessing such properties, and in each instance the preferred material for the particular supporting and enclosing means will be disclosed, e.g., the component holder 34 is preferably constructed of polyethylene.

The component holder 34 is supported upon a cupshaped metallic baseplate 35 which is formed with an outward.y extending radial flange 36. An annular insulating disk 33 atfixed to the baseplate 35 is provided with a plurality of rearwardly extending pins 39 which protrude through apertures 40 in the baseplate 35 to allow electrical connections to be made from the deferred action type battery 42 within the sleeve 11 to the amplifier and thyratron circuit assemblies. After the electronic components of the amplifier and the thyratron circuits are wired together, the completed assembly is housed in a cylindrical metallic shield can 44, and the edge of the shield can 44 at the open end thereof is crimped over the radial flange 36 to enclose the amplifier and thyratron circuit assemblies. The electronic circuit assemblies within the shield can 44 are potted through an aper ture (not shown) in the closed front wall 45 of the can 44 with a plastic suitable for electronic applications, preferably polyethylene. The word potting as used in the present specification is intended to include the operation of injecting softened plastic into a chamber in which an electronic circuit assembly has been positioned so that the solidified plastic fills all the voids and spaces between the electronic components and completely encases the assembly. Among the advantages of such embedment of electronic circuits are elimination of the conventional chassis and the shock-proofing and hermetic sealing of the individual subassemblies of the fuze. After the pot ting operation a headed metallic sealing plug (not shown) is soldered in the aperture through which the amplifier and thyratron circuit assemblies are potted to complete the hermetic sealing thereof. The components of the amplifier and thyratron circuit assemblies are thus rigidly held in place by potting material which will not soften at the temperature encountered within the fuze during the firing of a projectile, and displacement and vibration of the components is substantially prevented, even under conditions of high inertia and high centrifugal force. The components are completely encased within a potting material having substantially zero water absorption, and the potted amplifier and thyratron circuit assemblies are housed in a completely closed metal can which shields them electrostatically from the oscillator. Variations in electrical performance of the amplifier due to changes in humidity are thus minimized. Nonconducting means for supporting and enclosing the electronic components of the oscillator and the thyratron circuit assemblies include the component holder 34 and the potting material within which these circuit assemblies are embedded.

A plurality of small, approximately cylindrical electronic components of the oscillator circuit, e.g., resistors 52, choke coils 53, and condensers (not shown), are disposed within parallel cylindrical cavities 55 provided in a frustrum-shaped nonconducting base 56 positioned against the front closed wall 45 of the shield can 44. The base 56 is formed of a plastic suitable for electronic applications, preferably polyethylene. Ground studs 57 projection welded or otherwise secured to the wall 45 extend through apertures 58 in the base 56, and electrical leads 59 from the electronic components of the oscillator are soldered to the ground studs 5'7 to hold the base 56 in position against the closed front wall 45 of the shield can 44.

An oscillator coil 60 is wound upon a spirally-grooved tubular coil form 61 molded of a plastic suitable for electronic applications, preferably polystyrene. The coil form 61 fits snugly within and abuts against an annular radial shoulder 62 provided in a cylindrical axial compartment 63 in the base 56. A subminiature type oscillator electron discharge tube 65 fits snugly within a sock 66 molded of a plastic suitable for electronic applications, preferably polyethylene. The sock 66 is disposed within the axial compartment 63 in the tubular coil form 61 and in the base 56 and extends into an indentation 67 provided in the front wall 45 of the shield can 44.

The antenna cap assembly comprises a conical plastic antenna cap support 69 molded within a thin-walled, conical, metallic antenna cap 70. The antenna cap 70 is conveniently fabricated of thin sheet steel, and plated with silver over a subcoating of copper. Apertures 71 are provided in the walls of the antenna cap 70 to reduce eddy current losses, and the wall of the antenna cap 70 surrounding two diametrically opposite apertures 71 is indented to form concavities 73. After the antenna cap '70 is positioned within a suitable mold cavity, a plastic suitable for electronic applications, preferably polystyrene, is injected in molten state into the interior of the antenna cap 70 to form the antenna cap support 69. The softened plastic which flows through the apertures 71 into the concavities 73 during the molding operation solidifies externally of the indented portions of the walls of the antenna cap 71 to effectively join the metal antenna cap 70 to the antenna cap support 69. A rearwardly extending circular flange 74 provided on the rear surface of the antenna cap support 69 fits snugly within the inner circumference of the tubular coil form 61. A central aperture 75 is provided axially in the antenna cap support 69, and an antenna lead wire 76 from the coil 60 passes through an aperture in the wall of the coil form 61 and then extends forward through the central aperture 75 where it is soldered to the antenna cap '70.

After the oscillator circuit connections are soldered, the assembled shield can 44, base 56, coil form 61 and antenna cap assembly are inserted into a cavity which has substantially the same shape as the interior of the front case assembly 10, and a plastic suitable for electronic applications, preferably polyethylene, is injected into the cavity. The plastic fills all the air spaces including the aperture 75 and completely encloses the electronic components and their mountings to rigidly fixe all parts in position. The resulting potted oscillator-amplifier unit 78 thus conforms to the interior of the hollowed front case assembly 10. The nonconducting means for supporting and enclosing the electronic components of the oscillator circuit assembly thus include the base 56, the tube sock 66, the coil form 61 as well as the antenna cap support 69 and the potting plastic which fills the voids and air spaces between and completely encases the components.

An internal thread 79 is cut in the inner periphery of the sleeve 11 near the rear end thereof to engage the external thread of an auxiliary detonator 88. An inwardly extending radial flange 82 is formed in the inner periphery of the sleeve 11 approximately one third of the length thereof from the rear end, and a fiat metallic diaphragm 33 is brazed or otherwise secured to the flange 82 to seal the rear end of the sleeve against entry of moisture.

Near the front end of the sleeve 11, the inner periphery increases abruptly in diameter to form an annular radial shoulder 84 (see FIG. 3), and a circumferential undercut 86 extending longitudinally of the sleeve 11 is provided near the outer circumference of the radial shoulder 84. After a rear fitting S7 and the battery 42 are inserted within the sleeve 11, an annular lead washer 88 is assembled against the radial shoulder 84, and the oscillatoramplifier unit 78 is positioned against the front edge of the sleeve 11 with the edge of the shield can 44 which is crimped over the flange 36 seated against the lead washer 88. Electrical connections between the battery 42 and the oscillator-amplifier unit 78 are completed through jacks 90 disposed at the front of the battery 42 to receive the pins 39 which extend through the baseplate 35. The front edge of the sleeve 11 is crimped over the outwardly extending flange 36 of the baseplate 35 in a crimping die. During the crimping operation the lead washer 88 is squeezed into the circumferential undercut 86 so that the lead conforms to the shape of the undercut 86 and remains under pressure in a fully confined space. This produces a hermetic seal across the front end of the sleeve 11, the effectiveness of which is not dependent upon the shape of the crimp or the pressures used. The potted oscillator-amplifier assembly 78 thus completely seals the front end of the sleeve 11 to provide a compartment within the casing of the fuze into which moisture cannot penetrate. The baseplate 35 is keyed to the sleeve 11 by a pin 91 which is afiixed to the outer circumference of the baseplate 35 near the rear end thereof. The pin 91 fits within a groove 93 provided in the sleeve 11 to prevent turning of the oscilaltor-amplifier unit 78, of the battery 42, or of the rear fitting 87 with respect to the sleeve 11.

As described hereinbefore, the potted oscillator-amplifier unit 78 is adapted to fit snugly within the hollowed front case assembly 10. An annular gasket 94 of a suitable elastic and compressible material, such as neoprene, and an annular metallic spacer 95 are assembled over the oscillator-amplifier unit 7 8 before the front case assembly 10 is threaded on the sleeve 11. As the front case assembly 10 is advanced toward the rear of the sleeve 11, the annular gasket 4 is compressed into the circumferential recess 21. The sleeve 11 and the front case assembly 11) are separated only by the fixed thickness of the metallic spacer 95 which is clamped between the crimped edge of the sleeve 11 and the radial shoulder 22 when the sleeve 11 and front case assembly 10 are solidly screwed together. The compressed gasket 94 thus forms a hermetic seal for the entire casing of the fuze at the joint between the sleeve 11 and the front case assembly 18. This waterproof joint acts as a secondary obstruction to the entry of moisture into the sleeve 11 from the front end thereof, reinforcing the seal formed by crimping the edge of the sleeve 11 over the radial flange 36.

Due to the necessarily large tolerances in the height of the potted oscillator-amplifier unit 78 and in the inside dimensions of the plastic nose tip 12, a relatively large empty space 96 often existed between these parts in fuzes heretofore manufactured. Consequently, considerable deformation of the unsupported plastic nose tip 12 occurred in a projectile hoist, and it appears that vibration of the oscillator-amplifier unit 78 within the nose portion 10 during the flight of a projectile may have been a cause of premature detonations of proximity fuzes. In the preferred embodiment of the invention, a fixed amount of a softened plastic suitable for electronic applications, preferably polyethylene, is fedinto the hollowed interior of the nose tip 12 before the oscillator-amplifier unit 78 is inserted into the front case assembly 10. The softened plastic fills the space 96 between the oscillator-amplifier unit 78 and the plastic nose tip 12 to reinforce the plastic nose tip 12 and to prevent movement of the oscillatoramplifier unit 78 within the nose portion of the fuze.

Incidentally,'the use of a conical inside antenna cap 76 which can be varied in length as desired to change the capacity coupling between the oscillator and the shell offer s great flexibility in oscillator design. The length of the coil form 61 can be varied inversely as the length of the antenna cap assembly in order to maintain constant length of the potted oscillator-amplifier unit 78.

It will be apparent from the foregoing description and the drawings that a radio-controlled proximity fuze has been described that exhibits maximum weatherproofing and mechanical strength. One feature of my invention includes the hermetic seal of the oscillator-amplifier unit 78 across the front of the seleeve portion of the fuze, the leakproof joint between the polytetrafluoroethylene nose tip 12 and the metallic intermediate member 13, and the compressed gasket 94 in the annular space between the nose and sleeve portions of the fuze to provide a hermetic seal therebetween. Such fabrication provides a fuze casing which is imperviable to moisture and, in addition, divides the fuze casing into two separate compartments both of which are hermetically sealed. The compressed gasket offers a second obstruction to the entry of moisture into the sleeve portion. This feature greatly improves the weatherproofing and results in a fuze which can be stored for considerably longer periods in humid climates without failure of condensers or variation in oscillator sensitivity than fuzes heretofore manufactured.

A second feature of the invention includes nonconducting supporting and enclosing means, as well as the means for cementing the oscillator-amplifier unit 78 to the conical nose tip 12, constructed of material having excellent electrical properties, substantially zero water absorption, and a sufficiently high melting point to prevent softening at the temperature encountered Within the fuze during the firing of a projectile. The nonconducting parts are either polyethylene or polystyrene. The individual electronic circuit assemblies are thus hermetically sealed Within a material that has substantially zero water absorption, the electronic components are supported with maximum rigidity and strength, and the entire oscillator-amplifier unit 78 is made substantially integral with the plastic nose tip 12. Consequently, the fuzes can be stored for longer periods of time under conditions of high relative humidity without resulting duddage than if only the first, i.e., imperviable fuze casing, feature of my invention is utilized, and duddage and premature detonations due to mechanical failure, displacement of components, or vibration is considerably lower than in fuzes heretofore manufactured.

Still a third feature of my invention includes the conical antenna cap 70 fitted tightly over the nonconducting front end of the oscillator-amplifier unit 78 in capacitive relation with the metallic portion of the fuze casing and within the hollowed nonconducting nose tip 12. The nose tip 12 is of polytetrafluorethylene which has zero water absorption and yet high enough impact strength so that the wall section thereof can be made thin enough to permit insertion of an antenna cap 70 of sufficient size so that the capacity coupling between oscillator and shell is not materially decreased in comparison with fuzes having exterior antenna caps. The antenna cap is encased within the hollowed nose tip where it is entirely shielded from air friction during the flight of a projectile, from the blast of the gun, and from the pawls and hammers of projectile hoists. Consequently duddage and premature detonations due to damaged antenna caps or to opening of the antenna connections are considerably reduced in comparison to prior art fuzes, and yet the radiation impedance into which the oscillator feeds is not appreciably increased above that of fuzes with exterior antenna caps.

While the embodiment of the present invention constitutes a preferred form, it is to be understood that other forms might be adopted, all within the scope of the claims which follow.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. A radio-controlled proximity fuze including a tubular sleeve closed at the rear end thereof and having a radial circumferential groove in the inner periphery near the front end thereof, the rear radial face of said groove being provided with an undercut extending longitudinally of said sleeve, a hollowed, approximately conical front case having an internal thread cut in the inner periphery near the rear open end thereof, an oscillator-amplifier unit adapted to fit snugly within the hollowed interior of the conical front case, said oscillator-amplifier unit having an outwardly extending radial flange adjacent the rear end thereof, said radial flange extending into said groove with a pressed fit, a gasket of flowable metal of larger volume than the undercut and deformed into said undercut by the pressed fit connection between said flange and said groove whereby a hermetic seal is formed across the front end of the sleeve between said groove and said flange, said sleeve having an external thread cut in the exterior periphery near the front end thereof to engage the internal thread in said front case, said front case having a circumferential recess cut in the inner periphery thereof in front of said internal thread with the front radial face of said recess extending further toward the axis of the front case than the minor diameter of said internal thread to form a radial shoulder which is adapted to abut against the front edge of the sleeve when the front case is threaded onto and advanced toward the rear end of the sleeve, an annular metallic spacer having an inner diameter approximately the same as that of said radial shoulder, said front case being solidly screwed onto said sleeve squeezing said annular spacer between the front edge of the sleeve and said radial shoulder and closing the annular volume defined by said recess, the outer circumference of said annular spacer and the front end of the sleeve, and an annular gasket of elastic and compressible material of normally larger volume than said annular volume compressed into said annular volume to form a hermetic seal between the sleeve and the front case.

2. A radio-controlled proximity fuze in accordance with claim 1 in which the front case consists of a hollowed, non-conducting conical nose tip and a hollowed, metallic intermediate member formed with said internal thread and said circumferential recess, and including means for effecting a hermetic seal between said nose tip and said intermediate member.

3. A radio-controlled proximity fuze in accordance with claim 2 in which said conical nose tip is constructed of polytetrafluoroethylene.

4. A radio-controlled fuze in accordance with claim 1 in which the front case consists of a hollowed, nonconducting, conical nose tip and a hollowed, approximately frustrum-shaped, metallic intermediate member, said intermediate member having said internal thread and said circumferential recess formed therein, the front edge of said intermediate member having an annular indentation therein extending rearwardly parallel to the axis of the intermediate member, the rear open end of the conical nose tip extending into said annular indentation with a pressed fit to form a hermetic seal between the nose tip and said intermediate member.

5. In a radio-controlled proximity fuze, a metallic fuze casing, a hollowed conical nonconducting nose tip rigidly engaging said casing, a conical plastic-embedded oscillator circuit unit including an oscillator coil adapted to fit snugly within said hollowed nose tip, and a thin-walled conical metallic antenna cap fitted tightly over said unit in capacitive coupling with said casing, said coil being electrically connected by a wire through said plastic to said cap.

6. A nose portion of a radio-controlled proximity fuze having a metal outside casing adapted to be threaded to the metal casing of an ordnance projectile at the front end thereof, including an oscillator coil spaced in front of and electrically grounded to the fuze casing, a conical insulating covering completely encasing the coil, a thinwalled, conical, metal antenna cap fitted tightly over the front of said covering in spaced and insulated relation to the metal fuze casing to form electrical capacitance therewith, a wire connecting the antenna cap through the covering to the coil, and a plastic conical nose tip fittirig tightly over the antenna cap and the covering and engaging the fuze casing rigidly whereby the antenna cap is completely surrounded by insulating material.

7. A nose piece for an ordnance projectile operated by a radio-controlled proximity fuze in which a metal antenna cap insulated and spaced from the metallic outside casing of said projectile capacity couples an oscillator to said casing, including an oscillator coil spaced in front of and electrically grounded to said metal casing, a conical plastic covering completely encasing said coil, a thinwalled, conical, metallic antenna cap fitted tightly over and molded to the front of said covering, the coil being electrically connected through the covering to the antenna cap, said cap being spaced in front of and insulated from said casing to form electrical capacitance therewith, a hallowed polytetrafluoroethylene conical nose tip fitting over the antenna cap and the covering and fastened securely to said casing, said antenna cap being spaced from the interior of said nose tip, and a plastic member adapted to occupy and completely fill the space between the antenna cap and the interior of said nose tip to form a tight connection therebetween when the former is inserted within the latter.

References Cited in the file of this patent UNITED STATES PATENTS Davidson et al Sept. 23, 1941 OTHER REFERENCES Shackleton: PolyethyleneA New Thermoplastic,

10 pages 99, 178, 180, Modern Plastics, February 1944.

Page et al.: Reprint from American Journal of Physics, vol. 15, No. 2, pages 95-410, March, April 1947.

Franklin et al.: Scientific American, December 1947, pages 258-260. 

5. IN A RADIO-CONTROLLED PROXIMITY FUZE, A METALLIC FUZE CASING, A HOLLOWED CONICAL NONCONDUCTING NOSE TIP RIGIDLY ENGAGING SAID CASING, A CONICAL PLASTIC-EMBEDDED OSCILLATOR CIRCUIT UNIT INCLUDING AN OSCILLATOR COIL ADAPTED TO FIT SNUGLY WITHIN SAID HOLLOWED NOSE TIP, AND A THIN-WALLED CONICAL METALLIC ANTENNA CAP FITTED TIGHTLY OVER SAID UNIT IN CAPACITIVE COUPLING WITH SAID CASING, SAID COIL BEING ELECTRICALLY CONNECTED BY A WIRE THROUGH SAID PLASTIC TO SAID CAP. 